The invention relates to a reformer for the generation of synthesis gas, equipped with a plurality of catalyst-filled reformer tubes suspended in a pressure vessel, at least a section of each reformer tube being provided with a jacket tube, the purpose of which is to form a duct for the product gas flowing upwards from a lower mixing chamber to the head space of the pressure vessel.
Reformers of this type are known, for example, from the applicant's patent specifications DE-35 32 413-A, DE-36 05 811-A or DE-38 13 864-A, whereas EP-0 171 786 or U.S. Pat. No. 4,337,170offer comparable solutions.
In such a technology for synthesis gas generation, convective reformers of this type are equipped with reformer tubes which are filled with catalyst. A mixture of steam and hydrocarbons is fed to these tubes, is heated therein, and thus is converted to a gas containing H.sub.2 and CO, its temperature at the outlet from the reformer tube being at least 680.degree. C. and the pressure being elevated. The heat required for the endothermal reaction is provided by another source. All such sources have in common for the present application that this source is a gas of a higher temperature than, and about the same pressure as, the gas leaving the reformer tubes, but the molar mass flow rate of which is mostly greater than that of the gas leaving the reformer tubes. A further feature is that the gas of said source is also a H.sub.2 /CO-bearing gas, but with a lower content of residual methane. The product gas used as heating gas is formed when the two streams are mixed before it is used as the source of heat for the reaction in the reformer tubes of the convective reformer.
Example
Gas at the outlet of the reformer tubes: molar mass flow rate=1059 kmol/h at a temperature of 700.degree. C. and a pressure of 21.1 bar. PA1 Gas from the heat source: molar mass flow rate of 2532 kmol/h at a temperature of 880.degree. C. and a pressure of 21.1 bar PA1 Mixture=product gas=heating gas: molar mass flow rate=3591 kmol/h at a temperature of 816.degree. C. and a pressure of 21.1 bar
To achieve the required yield of H.sub.2 and CO and, consequently, the required lowering of the residual methane content in the product gas, it is essential that all the reformer tubes of the convective reformer be heated as uniformly as possible, so that the residual methane contents of the gas streams leaving the individual reformer tubes differ from each other as little as possible.
It is assumed that suitable measures are employed to achieve a uniform gas distribution among the individual reformer tubes. This can be achieved, for instance, by installing defined pressure-reducing means in the feed lines, a method that is used, for example, in the construction of steam generators (installation of restriction orifice plates). For reasons of energy conservation, it is even more important to minimize the pressure drop on the shell side without impairing the efficiency of heat transfer.
The object of the invention is to find a solution, with the aid of which the mixing, in particular, of the ensuing streams is improved, while simultaneously equalizing the heat load, which acts on the reformer tubes, by mechanically simple and economical means.